Science / Periodic Table of Elements / Atomic Weight: Atomic weight values represent weighted average of the masses of all naturally occurring isotopes of an element. The values shown here are based on the IUPAC Commission determinations (Pure Appl. Chem. 73:667-683, 2001). The elements marked with an asterisk have no stable nuclides. For these elements the weight value shown represents the mass number of the longest-lived isotope of the element.
Weight Verb Synonyms: heaviness, avoirdupois, mass, tonnage, heft
Weight Noun Synonyms: arrange, manipulate, bias, incline, slant, rig
Science / Chemistry / Molecular Weight: The average mass of a molecule, calculated by summing the atomic weights of atoms in the molecular formula. Note that the words mass and weight are often used interchangeably in chemistry. MORE
Science / Chemistry / Formula Weight: The formula weight is the sum of the atomic weights of the atoms in an empirical formula. Formula weights are usually written in atomic mass units (u). MORE